Intercalation reactions in CuCl2-FeCl3 system

Abstract

The intercalation reactions in CuCl2-FeCl3 system were studied by gravimetric analysis, X-ray powder diffractometry and energy dispersive X-ray spectroscopy (EDS). The reactions between graphite and a mixture of CuCl2 and FeCl3, between CuCl2-GIC's and FeCl3, and also between FeCl3-GIC's and CuCl2 were examined at 300 and 550°C.At 300°C, where the de-intercalation of CuCl2 or FeCl3 from their GIC's in a sealed tube was negligibly small, it was found that FeCl3 is intercalated into vacant graphite galleries and also exchanged with CuCl2 existing in graphite interlayer spaces, while CuCl2 can be merely exchanged with FeCl3 in graphite interlayer spaces. At 550°C, however, the de-intercalation of the intercalates, the intercalation of CuCl2 or FeCl3 into the vacant graphite galleries and the exchange reaction between FeCl3 and CuCl2 proceeded simultaneously. The formation of a molten salt in the CuCl2-FeCl3 system was observed, which seemed to lower the reactivities of CuCl2 and FeCl3 to graphite. The results of the line analysis by EDS showed that CuCl2 and FeCl3 intercalated seemed to coexist in separated domains. From the present results, the following four processes seemed to affect the formation of the ternary GIC's (Fig. 2); (1) exchange reaction between intercalates and reagents, (2) intercalation of reagents into vacant graphite galleries, (3) de-intercalation reaction from the starting GIC's and (4) formation of molten salt which seemed to lower the reactivities of metal chlorides.